Crystalline monozinc formaldehyde sulfoxylate.



UNITED STATES PATENT ornron.

MAX BAZLEN, Emir. n nenn, AND

moron wonnrnnn'r, or nunwresnnrnnson- THE-RHINE, GERMANY, ASSIGKOBS IO TBADISCHE I ANILIN 8c SODA FABBIK, 01"

LUDWIGSHAFEN-ON-THE-RHINE CRYSTALLINE MONOZINC No Drawing.

Specification of Letters Patent.

GEBMALBTI, A CORPORATION.

ronmnnmn SULFOXYLATE.

Patented May 27, 1913.

Application nearebruar 20, 1912. Serial No. 678,865.

To all whom, it may concern:

B it known that we, MAX BAznEN, Emil RIEGER, and THnooon- WOHLFAHRT, subjects, respectively, the first and third of the King of Wurttemberg and the second of the King of Prussia, residing at Ludwigshafen-on-the'-Rhine, Germany, -have .invented new and useful Improvements in Crystalline Monozinc Formaldehyde Sulfoxylate, of which the' following is a specifi- I cation.

' such solution be It is known that the di-zinc salt of formaldehyde sulfoxylic acid (of a constitution corresponding to the formula ZnSO .CH O) can be obtained in the solid state both in the anhydrous form and also containing. water of crystallization (see Bcm'chte, 1909, vol. 42, p. 4637). It is placed on the market in the form of a difiicultlyv soluble powder under the'name of decroline. By evaporating a solution of the mono-zinc salt of formaldehyde sulfoxylic acid, either alone, or in admixture with another salt, thick syrups have been obtained which, in some cases, on cooling, set to a hard glassy mass.

We have found that mono-zinc hyde sulfoxylate can be obtained in the crystalline form. from a solution thereof, if.

evaporated, preferably under reduced pressure at the temperature of the boiling water bath, and carev be taken when the solution. has reached the point of saturation it is brought into contact with a crystal of mono -'zinc. formaldehyde sulfoxylate. Such crystals can be produced initially by stirring a very concentrated solution of zinc formaldehyde hydrosulfite' with alcohol, whereupon mono-zinc formaldehyde sulfoxylate is precipitated in crystalline form, while zinc formaldehyde-bisulfite remains in solution. When once the manufacture has been started, the crystals floating in the air, or from different parts of the apparatus are "often. sufiicientf tov crystals in a oxylate has commenced, it is and the said crystals formalde I remains in the mother liquor and can aidof therequisite quantity of acid'to give rise to the mono-zinc salt.

pre erred to continue the evaporation until it is found' that no considerable increase in the quantity of crystals takes place, The crystals are then. separated, which may be done either by filtration o-r by centrifugal action, are preferably washed with alcohol and dried in 'vacuo.

The crystals of mono-zinc formaldehyde sulfoxylate are vthus produced free from water of crystallization and. have a con;

Zn(HSO .CH O) and cellent keeping power. insoluble in alcohol.

at 20 Gabe prepared containing about 70 partsof the salt to 100 parts of water, on allowing this solution to stand a large quanhave, when dry, ex-' They-are practically rates'out, these having a constitution correspondmg to the formula while if 100 parts of the anhydrous salt be dissolved in 100 parts of water at 60 0., a salt containing three molecular proportions of Water of crystallization crystallizes out in pearly leaflets. Neither of the forms containing water of crystallization'is, however, so stable asis the anhydrous form.

In carrying out'our invention, either pure solutions of the mono-zinc salt, or solutions which contain other salt orsalts in addition to the said mono-zinc salt can be employed.

One simple. method of carrying out our institution corresponding to the formula- If a solution in water tity of small rhombohedral crystals sepavention consists in evaporating a solution .85

of the; easily available zinc formaldehyde hydrosulfite, so that mono-zinc formaldehyde sulf oxylate is. obtained in the crystalline form, while zinc formaldehyde. bisulfite employed for any required purpose. All? other method of carrying out our invention consists in employing solutions prepared by dissolving the di-zinc salt in water with the Or the monosodium formaldehyde sulfoxylate- 'can be treated'with a zinc salt in aqueous solution,

ate

and then, upon evaporation, if zinc sul has been employed, sodium sulfate first separates out and can be removed, or if zinc chlorid has been used the sodium chlorid been" remains in solution while, in

either-case, the mono-zinc formaldehyde sulfoxylate is obtained in the crystalline form.

Mono-zinc formaldehyde sulfoxylate, on-

account of its solubility, can be employed with advantage ln'many cases where the use of the di-zinc salt is not so advantageous.-

Our new compound is capable of reducing 262 grams of indigo for every 32 grams of sulfur contained therein,

Now what we claim is:

Crystalline mono-zinc formaldehyde sulf-. oxylate which in the pure state and free from water of crystallization possesses a composltion corresponding to the formula Zn(HSO .CH O) 

